This invention relates to a robot control system for operating a robot in accordance with positional information in the form of rectangular coordinates, the robot having a hand which operates on the basis of cylindrical coordinates, more particularly, the invention relates to a robot control system wherein a robot which operates in a cylindrical coordinate system is taught using a rectangular coordinate system.
In recent years, robots have come into widespread use on assembly lines and a variety of such robots have been proposed. These robots come equipped with a hand which, for the sake of simplifying control, is controlled on the basis of a cylindrical coordinate system.
A robot, specifically with the robot hand, responds to requests from a machine tool by performing a variety of services such as loading and unloading a workpiece to and from the machine tool as well as changing tools, on the basis of robot command data which is taught or edited in advance. FIG. 1 is a block diagram of a conventional robot control system of this kind. In FIG. 1, numeral 11 denotes a robot control device comprising a computer and having a processor 11a comprising a microcomputer or the like, a control program memory 11b for controlling teaching, playback, editing and the like, a data memory 11c for storing robot command data created on the basis of data entered from a teaching box 12 to be described later, and a working memory 11d for storing the current position, along each axis, of the robot hand which operates in a cylindrical coordinate system, and for storing data memory addresses, the operating speed of the hand, service codes indicating the kind of service to be performed by the robot, etc. The data memory 11c includes minor regions at addresses 0 to 299, each minor region storing robot command data comprising operating speed V0, coordinates that indicate the position of a commanded point, namely coordinates R0 (position along the direction of arm extension and retraction), Z0 (position along the vertical direction), .theta.0 (position along the direction of swiveling), as well as a maximum of five service codes for services executed at the commanded point, as shown in FIG. 2 which is an illustrative view of a storage region in data memory 11c. Numeral 12 denotes the teaching box having various buttons, for teaching robot operations, as well as numerical devices, etc. Numeral 13 denotes a robot which operates on the basis of a cylindrical coordinate system. Numerals 14, 15 and 16 denote machine tools, such as lathes, serviced by the robot.
In general, a teaching operation in a robot control system of the above kind proceeds in the following order:
(1) Select the teach operation--Establish the teach mode by operating job selection buttons (not shown) on the teaching box 12.
(2) Set address--Enter, by means of a ten-key pad on the teaching box 12, the address of the location of the data memory 11c at which the robot command data is to be stored, and set the address in an address register of the working memory 11d.
(3) Teach position and operating speed--After an address has been set, move the robot hand to and position it at a commanded point by depressing the buttons on the teaching box 12 one at a time, namely +R and -R jog buttons for the R-axis, +Z and -Z jog buttons for the Z-axis, or +.theta. and -.theta. jog buttons for the .theta.-axis. As each jog button is depressed the robot hand moves along the axis specified by the depressed jog button. At such time, pulses for moving the robot hand are generated within the robot control device. These pulses are counted up or counted down by prescribed current position counters of the working memory 11d in accordance with the direction of movement. That is, the current position of the hand is stored in current position counters, one for each axis, at all times. Next, enter the operating speed by means of the ten-key pad on the teaching box 12 to store it in a speed register of the working memory 11d. When a position teach button on the teaching box 12 is depressed, the position of the commanded point on each axis (the contents of the current position counters), and the speed at which the hand is to be moved to the commanded point, are stored at the set address.
(4) After teaching the position and operating speed, enter the robot actions to be executed at the commanded point, in the form of service codes (S-codes), by means of the ten-key pad on the teaching box 12. When an S-code button on the teaching box 12 is depressed, the S-code is stored in an S-code storage area at the above-mentioned address.
(5) Repeating the steps (1) through (4) ends the teaching operation for prescribed robot actions.
Thus, with the conventional teaching operation the position of the commanded point is taught by operating, one after another, the jog buttons for each axis of the cylindrical coordinate system. Since the teaching operation must be performed for each and every machine tool, the operation is extremely troublesome. In particular, in the case of a lathe or the like, the hand must be moved at right angles to the chuck surface in order to load and unload a workpiece in a reliable fashion. Teaching such movement using the conventional cylindrical coordinate system is very troublesome.
Accordingly, an object of the present invention is to provide a robot control system which enables a robot that operates in a cylindrical coordinate system to be taught using a rectangular coordinate system.
Another object of the present invention is to provide a robot control system which enables what is taught in a rectangular coordinate system at one commanded point to be utilized at another commanded point as well.